Query processing method of name-value pairs in relational databases

摘要

Electronic marketplaces typically apply catalog schema in the format of name-value pairs to store product attribute names and values to achieve a very high degree of flexibility. This vertical schema approach prevents traditional relational database management systems from accurately estimating constraint selectivity and generating efficient query plans. In this invention, methods and systems are disclosed for building and maintaining external histograms and a query planner uses these external histograms to assist query planning in relational databases.